The Arbiter episode contradicts Cole Protocol, the Hasley rescue contradicts the open statement in First Strike that Hasley had never been captured and First Strike kills all but a handful of Spartans who are completely accounted for until a point in which they go through a portal and there are no covenant, the history lesson Cortana gives contradicts the story in Cryptum, the clone episode contradicts the statement in Fall of Reach that none of the clones would live more than a few days, in character the episode with the emotionless sergeant is out of place given he pilots a fully functional weapon the UNSC was going to blow up when in every game and book they've done insane things to keep such tech intact. The only one that isn't contradicted at all is the first one with the marines and Spartan not getting along. They may label them canon but Bungie wasn't involved at all with this, it was a Microsoft/343 project, so I'm inclined to go with the more traditional stories that fit with the series. Still fun to watch some of them though.